1. Field of the Invention
The present invention relates to a finisher and a sheet aligning/stapling method, and more particularly, to a finisher for delivering sheets ejected from an image forming machine to bins and stapling the sheets in the bins, and an aligning/stapling method in the finisher.
2. Description of Related Art
Recently, various types of sorters (finishers) for delivering image-formed sheets to bins have been developed as optional attachments for image forming machines, such as copying machines and printers. Further, in order to comply with a demand for automation of sheet handling, sorters with a stapling function as well as a sorting function have been developed.
The present inventors invented a stapler-sorter wherein while a plurality of bins which are arranged one upon another at intervals of a specified distance are wholly moved upward and downward step by step, each sheet is handed into each bin on a specified level. In the stapler-sorter, for space-saving, it is preferred to set a stapler immediately above the sheet hand-out level. Further, in order to shorten the time for sorting operation, reciprocating distribution is adopted. Every time a group of sheets have been distributed to the bins, the movement of the bins is changed from an upward movement to a downward movement and vise versa. For example, copy sheets of an odd page are distributed to the bins while the bins are moved upward, and copy sheets of an even page are distributed to the bins while the bins are moved downward.
In the stapler-sorter, the order of bins of being subjected to stapling operation after sorting operation is related to the time for stapling operation. For example, if the stapler-sorter is so structured that sorting operation is carried out in the reciprocating distribution as the above example and that stapling operation starts with the uppermost bin in any case, in a case wherein sorting operation finishes with copy sheets of an odd page, stapling operation thereafter takes a long time. When the sorting operation finishes, the uppermost bin is above the stapler, and the bins must be moved downward before starting stapling operation.
Also, sheets distributed to the bins must be aligned in the respective bins for stapling operation, and sheet aligning in each bin must be carried out promptly so as not to intervene sheet transporting/distributing operation.